Dynamics Processor (Gate, Compressor & Limiter) for the Teensy OpenAudio Library https://github.com/chipaudette/OpenAudio_ArduinoLibrary
This effect is lousely based on my recollection of the venerable dBX1086 compressor, minus the de-esser stuff. Input 0 is the main signal input; Input 1 is used for side-chaining into the detctor, if so desired. The signal from Input 0 will be used if nothing is connected there.